Kid Ink FanThreatens to Sue Over ...On Stage Ass Whupping!

12/8/2015 12:44 PM PST

Kid Ink tells us the incident with Junior was "the second time a fan had jumped on stage during that particular show in Brazil, the first fan almost knocking me over! In the moment, my security was doing his job of protecting me and ensuring my safety."

He added that his security has been on high alert "due to what happened at The Bataclan in Paris a few weeks ago." Kid apologized for the way it played out and said he never wants to "to see any of my fans hurt or harmed at one of my shows, especially a young fan who has been a real supporter of mine like Junior."A Kid Ink fan says he'll sue the rapper and his bodyguard, who sent him flying through the air at a recent concert ... UNLESS he gets an apology.

We got footage of 18-year-old Junior Parriera catching major air -- a bird's eye view and from Junior's own phone -- at Ink's Sunday show in Sao Paulo ... and it looks like it hurt. A lot.

A video posted by The Official #WSHH Page (@realwshh) on Dec 7, 2015 at 12:37pm PST

Junior tells TMZ he's a huge fan and admits he got lost in the moment when he rushed the stage -- but he thinks the bodyguard, Bigg Chuck, went too far.

Junior says he's already spoken to lawyers and plans to sue Kid Ink and Chuck, more for the public humiliation than his injuries ... which he says were a little back pain and a hurt hip. Still, he says he'll let it be for the price of an "I'm sorry."